Inside Frequency Control

Swept quartz crystals are necessary in timing applications that require radiation resistance, but it's important to understand how they work and when you should use them. 

In this blog, we'll review what swept quartz crystals are, how they're manufactured, their common applications, and a common misconception about their benefits.

The process of buying crystal oscillators can be a headache if you don't know what to expect. But learning the basics of how to procure frequency control devices can help you plan accordingly and reduce your frustration. 

There are three main things you should know about crystal oscillators and frequency control devices when ordering them:

1. They have long lead times
2. They typically have a long shelf life
3. They have large purchased lot sizes

Let's dive a little deeper into each of these to give you a better idea of how they'll impact your purchasing strategy. We'll keep this blog short and to the point, but if you want to learn more, we've included links to our more in-depth articles on each topic.

When it comes to NTP stratum levels and minimum performance requirements for digital network synchronization, there's definitely a lot to know. A standard first released in 1987 entitled "Synchronization Interface Standards for Digital Networks" from the American National Standards Institute (ANSI) lays out all the official information and requirements. 

With the advances of RF technology over the last many years, most modern spectrum analyzers can now automatically detect changes in phase noise levels (mostly of sine wave signals) measured in units of dBc or rads.

But it’s always a good idea for RF engineers to understand how modern spectrum analyzers measure integrated phase deviation. Or better yet, for them to understand how to optimize a spectrum analyzer’s measurements even further. Believe it or not, but many spectrum analyzer readings of phase noise can be significantly off.

Measuring phase noise deviations is easier than it sounds. All you really have to do is learn how to determine the Root Mean Square (RMS). This is done by calculating the ratio of power from the single-sideband (SSB) phase noise to the carrier.

Here’s the scary thing…

Even if you sit for hours upon hours trying to set a precise initial frequency of an oscillator, it’s still going to drift and the oscillator will not be able maintain that frequency over the full course of its use. In this post, you’ll learn the many sources of frequency instability and why an ultra-stable OCXO may be the fix-all solution.

The #1 Most Critical Factor in High-End Radar & Communication Systems: Low Phase Noise

Phase noise, phase noise, phase noise.

If you’re involved with the design and implementation of communication systems, you most likely hear the term “phase noise” all the time (maybe more times than you’d like). 

There’s a good reason for all this phase noise chat. It’s one of the key factors that determines the overall success or failure of your radar or communications application. It’s even more important in intense environments where strong vibration or g-force is a concern.

Why is maintaining low phase noise such a concern in these applications and environments? And how can you solve the problems associated with the effects of phase noise? By the end of this article, you'll know why and how you should decrease phase noise in your applications.

The harsh truth is, selecting the wrong quartz crystal oscillator can quickly kill any design. With the wide variety of options and specs available on the market today, selecting the perfect crystal oscillator for your design can be a difficult and time-consuming task.

What's better than a crystal oscillator? A crystal oscillator combined with electronic frequency control (EFC)!

Of course, determining if EFC would be a good addition to your crystal oscillator circuit design (and if so, which method is best for you) comes down to your specific application and its requirements.

There are four options to choose from when selecting an electronic frequency control method for your crystal oscillator:

1. Pulse width modulation (PWM) & low-pass filter (LPF)
2. Reference RF signal & phase locked loop (PLL)
3. Voltage divide
4. Digital-to-analog converter (DAC)

In this post,  we'll take a closer look at each option and their best applications.

What if we told you that specifying more electronic frequency control (EFC) than you need could actually be hurting your company's wallet? Well, it very well may be!

Paying attention to whether your supplier is using AT-cut or SC-cut crystals will help you save money in the long run when it comes to oscillators. In this article, we'll review the difference between these two types of cuts and the impacts of EFC pull. 

Frequency perturbations, also referred to as activity dips, can be difficult to spot in crystal oscillators. But a single perturbation can cause major problems in an application’s signal, including within GPS or missile systems.

Imagine launching a missile and then losing control of its navigation. Or getting a very inaccurate GPS velocity reading of an aircraft. These (and many other problems) can be caused by a failure to spot activity dips in crystals.

In this article, we'll help you  understand what frequency perturbations are and how to prevent them from occurring in crystal oscillators.